Load-changeover switches of the kind described in the introduction are incorporated in on-load tap changers and serve for successive, rapid and uninterrupted switching over from the connected winding tap to the new, preselected winding tap. The entire on-load tap changer is actuated by a motor drive for the changeover. A rotating drive shaft continuously moves a selector and at the same time a force-storage unit of the load-changeover switch is loaded. The selector serves for power-free selection of the respective new winding tap of the transformer that is to be switched to.
In the case of the described load changeover the load-changeover switch executes a specific switching sequence, i.e. different switch contacts and resistance switchss are actuated in a specific succession in time in succession or with an overlap. The switch contacts in that case serve for direct connection of the respective winding tap with the load diverter and the resistance switchss for temporary connection, i.e. bridging over by means of one or more switch-over resistances. Vacuum interrupters are advantageously used as switching elements for the load changeover. This is due to the fact the use of vacuum interrupters for the load changeover prevents formation of arcs in the oil and thus oil contamination of the oil in the load-changeover switch.
A load-changeover switch of that kind is disclosed in German published specification DE 10 2009 043 171 [US 2012/0139510]. Here, the load-changeover switch carries a drive shaft with at least one cam disc. The cam disc has several control cams, wherein two control cams arranged at the cam disc at the end have a profile, which departs from a circular shape, in the form of lobes at each of which a respective roller, which is connected by way of a rocker with a vacuum interrupter and the profile contour of which scans the respective control cam, is guided with maintained contact.